1. Field of the Invention
The invention relates to a circuit board and a manufacturing method thereof. More particularly, the invention relates to a circuit board having circuits formed by two different conductive layers within the same circuit layer and a manufacturing method thereof.
2. Description of Related Art
Currently, the technology of a circuit board has evolved from a conventional non-embedded circuit board to an embedded circuit board. In particular, the conventional non-embedded circuit board is characterized in that circuits therein protrude from a surface of a dielectric layer. By contrast, circuits of the embedded circuit board are buried in the dielectric layer. Currently, a circuit structure of the circuit board is usually formed by performing a photolithography and etching process or a laser ablating process.
A process of forming build-up circuits of the embedded circuit board by the laser ablating process is taken as an example and includes the following. A dielectric layer is provided at first. Next, the surface of the dielectric layer is irradiated by a laser beam, so as to form an intaglio pattern and a blind via. Thereafter, an electroplating process is performed to form a conductive material layer filling the blind via and the intaglio pattern. Up to this point, a structure of the build-up circuits of the embedded circuit board has been completed in general.
However, a conventional conductive material layer has to have a certain thickness in order to fill up the blind via. In addition, when forming the conductive material layer by electroplating, the electroplating may not be performed evenly, such that the conductive material layer is not distributed evenly with an even thickness. Thus, when removing a portion of the conductive material layer outside of the blind via and the intaglio pattern, the thickness removed from the conductive material layer is hard to be controlled. Consequently, the embedded circuit layer can be thinned improperly in the removal. Moreover, a portion of the conductive material layer can be remained improperly to cause a short-circuit between circuits of the embedded circuit layer. Furthermore, the aforementioned issue becomes more obvious when the circuits of the embedded circuit layer are fine lines.